Which Asus H81 board? There are loads of them. I am trying to build up a list of which ones clock the G3258.

Just built this combo a few days ago. Couldn't work out how the hell to change the multiplier in the BIOS from "Auto". This was on BIOS 2105.
So I downgraded it to 2001 using EZFlash.
Still the same.
Until i figured out you had to actually type in 43 in the box !!!!!!!!!!!
Can't confirm that 2105 was able to overclock, but theres no extra/missing settings since downgrading it so my bet is that you'll be ok.
Seem stable enough though, so gonna leave alone.